Research
(last updated September 2023)
Research Overview
I have many ongoing projects in my lab. While I get up in the morning excited to learn answers to big, general ecological questions that span environments and taxa, I generally do my empirical work in grasslands and with grasses, aphids, and viruses. Much of my work examines the influence of the amount and ratios (i.e. ecological stoichiometry) of elements (like nitrogen and phosphorus) on species interactions, so the insights coming out of my lab often sit on the fence between community and ecosystem ecology. While there is often quite a bit of intellectual cross-over among my projects, broadly they can be categorized into a few areas.
The Nutrient Network or NutNet project (blue & red in figure), co-founded by myself and a few others in 2007, is a distributed, collaborative experiment currently being replicated by investigators at more than 170 grassland sites in 29 countries spanning 6 continents. At each site, scientists erect fences to change grazer density and experimentally add nutrient fertilizers using the same methods at every site.
The DRAGNet project (gray and red in figure), or Disturbance and Recovery Across global Grasslands, co-founded by myself and a few others in 2020, is quantifying disturbance impacts on herbaceous plant community reassembly and ecosystem recovery under ambient and elevated soil nutrient supply. In this experiment, scientists experimentally add nutrient fertilizers and impose 3 years of soil disturbance using the same methods at every site. DRAGNet is interoperable with NutNet (same plot size, core data, and methods for measuring responses), with two shared treatments, opening opportunities for more exciting questions. It is currently has 93 contributing sites in 32 countries.
Because the treatments are exactly replicated at each site, the responses we measure can be directly compared and differences in responses among sites can be attributed to biology, rather than methodology.
These coordinated, long-term experimental research projects led out of the Borer-Seabloom lab at the University of Minnesota are generating new understanding of the extent - and the conditions under which - multiple resource limitation, consumers, and physical soil disturbance control the dynamics and functioning of the world's grassland ecosystems. This project is rockin' fun in addition to producing cool new insights.
Even though three of the most globally-pervasive human impacts are (1) changing supplies of the resources that limit primary production (e.g. burning fossil fuels and putting nitrogen and carbon in the atmosphere), (2) changes in the abundance and identity of consumers (e.g. trading cows and sheep for native grazers), and (3) soil disturbance by animals and humans, the Nutrient Network (aka NutNet) and DRAGNet represent the first globally coordinated experiments to quantify the effects of these changes on ecological systems.
Many researchers around the world are leveraging this experimental infrastructure to measure new responses and tackle novel questions. One particularly exciting project is a multi-university collaboration between the Borer-Seabloom lab at the University of Minnesota, the Zhou lab at Oklahoma, and the (Yunfeng) Yang lab at Tsinghua University to test hypotheses about how nutrients modify links between soil microbial diversity and function.
Community & ecosystem ecology of microbes - including disease
The fungal, bacterial, and viral microbes inhabiting all free-living organisms are extremely diverse and encode the vast majority of genes in the biosphere. Microbes in a human, for example, account for 100 times more genes than their host; similar results are emerging for virtually all free-living organisms. Disease is the best studied host-microbe interaction, but microbes in hosts also are responsible for critical functions, including nutrient uptake (plants and animals), reduction in inflammatory responses (animals), digestion (animals), anti-herbivore defenses (plants), and pathogen resistance. Right now in this area of research, it seems that the more we look at microbial diversity and functional significance in hosts, the more we find.
Much of the work in this area has focused on microbes and their hosts, but I am interested in how other considerations -- host nutrition, predation, or disease transmission from dead hosts -- may fundamentally change our predictions about microbial communities
in hosts. My work in this area includes studying the effects of resource availability (i.e., host nutrition), competition among hosts, and consumers (like herbivores) on infection transmission, host-microbe interactions, and microbial diversity in hosts. I am also tackling the ecosystem effects of disease on nutrient recycling.
Pathogens & disease. I have spent nearly two decades studying the long-term implications of an aphid-vectored disease, barley yellow dwarf virus (BYDV), on US West Coast grassland community composition and the role of environmental change on BYDV transmission and virus communities. Using this model system, my group has worked on topics from virus biogeography to nutrition, vector behavior, and competition among viruses sharing a host.
Whole microbial communities. I am also collaborating with researchers using metagenomics across the Nutrient Network to better understand the factors controlling the composition of the microbial communities within hosts and in the soil, the effects of these microbes on plant communities, and the spatial scales at which nutrients and herbivores control microbes in natural systems. We are currently focusing primarily on fungi and prokaryotes (e.g., bacteria).
Pathogens and nutrient recycling. I also have a SESYNC-funded project developing a theoretical basis for the ecosystem ecology of disease. We are developing new mathematical theory to examine how the supply of nitrogen may alter disease and disease may, in turn, alter the ecosystem-scale cycling rates of nitrogen and carbon.
Plant-insect interactions
Some of my lab's work includes analyses of new and existing datasets on insect diversity responses to experimental changes in plant diversity and environmental nutrients and the role of insects on plant composition and net productivity. We examine diversity and interactions through many lenses, including evolutionary associations and chemical fluxes, and we ask questions about insect and plant interactions with other food web members, including microbes. Much of this work is being done at Cedar Creek Ecosystem Science Reserve.